The present invention is directed to a highway barrier and parapet and a method for assembling a highway barrier and parapet.
In highway and roadway construction, a median barrier or barriers is often attached to a bridge or road surface to separate various lanes of traffic. The bridge or roadway may also include a parapet or parapets located on the outer edges of bridge or road surface to protect pedestrians from traffic and maintain traffic on the bridge. The median barriers and parapets may be a xe2x80x9csafety shapexe2x80x9d system, which are median barriers or parapets having a profile that allows smooth mounting and demounting of a vehicle along the lower edges of the barrier or parapet. An example of such safety shape median barrier systems are metal median barriers are manufactured by Dow Chemical Company of Midland, Mich. and by Magnode Products Company of Trenton, Ohio.
Safety shape median barriers and parapets usually have a generally smooth, continuous outer surface. The outer surface has a lower edge forming an angle with, and located adjacent to, the road surface. When a vehicle veers off the roadway and onto the safety shape median barrier or parapet, a wheel or wheels of the vehicle ride up on the lower edge of the median barrier or parapet. As the vehicle continues to ride up the median barrier or parapet, the vehicle is guided upwardly and rotated away from the barrier by the shape of the barrier or parapet. The upward and rotational movement of the vehicle converts some of the lateral energy of the vehicle into a vertical component which can be absorbed by the vehicle springs. The safety shape median barriers or parapets are also shaped to smoothly guide the vehicle from the median barrier or parapet back onto the roadway.
The existing safety shape median barriers and parapets, while most frequently made of concrete, can also be made of extruded metal panels that are attached to vertically extending posts, and are particularly used on bridges or other elevated roadways. Most existing metal safety shape parapet or median barrier systems are installed by aligning pre-drilled holes in the panels with pre-drilled holes in the posts, and then passing a fastener through the aligned holes. However, it is difficult and time consuming to align the predrilled holes, as the panel elements may be warped or distorted, the posts may not be precisely located in the desired location, and/or the dimensions of the posts and panels may vary due to thermal expansion or contraction. Another drawback with existing median barrier and parapet systems is that the panels include access holes through which the fasteners are passed to enable assembly of the system. These access holes are unsightly and can allow debris or wildlife to enter the barrier or parapet.
During installing of existing highway safety shape median barriers or parapets, a foot piece is typically coupled to the deck. Several bolts are passed through the foot piece to attach the foot piece to the deck. The panels are then slid laterally into a slot in the foot pieces to couple the panel and the foot pieces together. However, sliding the panels into the foot pieces can be difficult and time consuming due to the size of the panels, friction between the panels/foot pieces and warping or distortion of the materials. Furthermore, once the panel is coupled to the foot piece in this manner, the panel typically blocks access to the bolts that couple the foot piece to the deck, which increases assembly time.
A further drawback with many prior art safety shape median barrier and parapet systems is that they are intermittent; that is, there are regularly spaced discontinuities along the length of the system. Because most prior art safety shape median barrier systems rely upon the alignment of pre-drilled holes, as more panels are mounted it becomes increasingly difficult to mount the panels to the posts due to the accumulated out-of-range tolerances. Accordingly, it is often necessary to create a break in the system (i.e., a discontinuity) in a vertical plane. A new post is then mounted adjacent to the existing post, and a new section of panels are restarted to reset the out-of-tolerance measurements. However, the discontinuities formed by this method of construction may create areas of weakness at the discontinuities. Furthermore, the discontinuities create a series of discreet, structurally independent sections within the median barrier or parapet system. Each section has little ability to transfer impact loads to its adjacent sections, and therefore each section of the median barrier or parapet system stands alone when receiving an applied force.
In order to address this problem, metal plates may be bolted to the median barrier or parapet and located such that the plates extend over a discontinuity. Alternately or additionally, the median barrier or parapet may include an upper section of railing that bridges the discontinuity. While providing some segment-to-segment continuity, these measures do not significantly address the loss of continuity in such median barrier or parapet sections.
Accordingly, there is a need for a safety shape median barrier or parapet system that is easy to install, and provides flexibility during installation by accommodating variations in the dimensions and locations of various system components. There is also a need for a safety shape median barrier or parapet system that provides ready access to the bolts that attach the system to the deck, and that reduces the effect of vertical discontinuities in the system.
The present invention is a safety shape median barrier and a parapet system that is easy to install, accommodates size variations in various components, provides ready access to the mounting bolts during installation, and reduces the effect of vertical discontinuities in the system. More particularly, the present invention utilizes a plurality of panels, each panel including one or more channels shaped to receive a clamp bar therein. The clamp bars can be slid within the channels and mounted to a post or other structure by a fastener. Because the clamp bar is free to slide within the panels, the panels need not have pre-drilled holes. The channel/clamp bar system enables the panels to be attached to the posts or other structures at nearly any point along the length of the panel, and provides a high degree of flexibility to the installer. Because there is no buildup of out-of-range tolerances in the median barrier or parapet of the present invention, the median barrier or parapet can be installed as a substantially continuous system.
The various components of the present invention can be arranged such that discontinuities in a layer of components of the system are spanned by the structure of an adjacent component. In this manner, the system can be assembled so that there are no discontinuities that extend throughout the height of the median barrier or parapet system, which increases the strength of the median barrier or parapet.
In one embodiment, the present invention includes a plurality of base plates that are coupled to the bottom of the posts, and the base plates are shaped to receive the bottom of the lower panels. Because each base plate has a fixed distance between its outer edges and the post, the base plates precisely set the lateral spacing of the lower panels. In this matter, the tolerances in the system and the loading bearing characteristics of the system can be tightly controlled. The base plates also help to transmit applied loads into tensile and compressive forces to improve the load bearing characteristic of the median barrier or parapet system.
In another embodiment, the present invention also includes a support element that receives a panel therein to couple the panel to the deck. The support element is attached to the deck by one or more bolts, and includes an inwardly opening end surface that receives a lower flange of the panel therein. The support element enables the panel to rotate out of the vertical plane of the mounting bolt and thereby provides access for tightening of the bolt.
In one embodiment, the invention is a parapet for mounting on a deck and resisting applied loads comprising a base plate located on the deck and a post coupled to the base plate and extending generally upwardly from the deck. The parapet further includes a lower panel pivotably coupled to the base plate and the lower panel form a triangular truss for resisting applied loads.